Experimental Study of a Novel Testing Platform for the Thermal Performance of Solar Domestic Water Heating Systems

Solar domestic water heating systems (SDWHS) are widely used in China, with an installed collector area of more than 330 million square meters by the end of 2014.Many relevant products keep on launching and upgrading in the market. To regulate the market, the performance of products, especially new products should be evaluated by thequality supervisionagency. However, all the existing national standards of thermal performance tests forSDWHSrequire that the daily solar irradiationgain should be more than 16 MJ/m2.Thus, only a small part of days in a year meet this criteria, which constrained quality supervisionagencies to regulate the solar heater market. A new approach of testing platform for the thermal performance of SDWHS is also presented in this manuscript. The testing platform consists of a sun-tracking flat-mirror reflector which not only directs the sunlight to the collector to increase the daily solar irradiation gain but also produces a light spot of 2×2 m2. A large number of experiments have been conducted to measure the performance of the testing platform. Results show that on one hand the platform can increase the daily gain of solar irradiation to 16 MJ/m2 from 12 MJ/m2, and on the other hand the light spot has a non-uniformity of less than 3%. Experiments onSDWHShavebeen performed on the platform as well as on the ground, respectively. It has been found that the relative difference of the daily thermal efficiency measured by the two methods is lower than 3%.